1. Field of the Invention
The present invention relates to a measurement system and measurement processing method.
2. Description of the Related Art
There has conventionally been known a pattern projection method of measuring a surface shape by irradiating a measurement target with pattern light. Various proposals have been made for a surface shape calculation method, pattern light control method, and the like.
For example, Japanese Patent No. 3847686 discloses an arrangement in which modulated pattern light is generated by switching micro-optical surfaces arrayed in a matrix in accordance with a predetermined modulation pattern, and the measurement target is irradiated with the modulated pattern light. Further, in an arrangement further disclosed in this reference, an irradiation image formed by focusing pattern light reflected by the measurement target is modulated to extract the light quantity change component of the irradiation image. Parallax information corresponding to the distance to the measurement target is calculated and output as the surface shape of the measurement target.
Japanese Patent Laid-Open No. 11-044515 discloses a technique of controlling pattern light. In this technique, the interval of straight stripe pattern light that has a wavelength outside the visible region and is emitted to acquire distance information to a measurement target, or the beam scanning interval is controlled based on acquired distance information.
Further, Japanese Patent Laid-Open No. 2006-292385 discloses an arrangement in which the measurement target is irradiated with pattern light. In this arrangement, the type and number of pattern light beams emitted by an optical space modulation element are adaptively controlled based on the feature amount of a sensed image or a change of the feature amount.
The techniques disclosed in these references are used to measure the surface shape of a measurement target. These references do not disclose an arrangement that measures the surface characteristics of a measurement target other than the surface shape.
In a method of measuring a surface shape by irradiating a measurement target with pattern light, like the pattern projection method, light reflected by the surface of the measurement target is not a little affected by the surface state of the measurement target.
For example, when the measurement target has a fine microstructure on the surface (smooth surface), the specular reflection component is dominant as a component contained in reflected light. To the contrary, when the measurement target has a rough microstructure on the surface (rough surface), the specular reflection component and scattering component coexist as components contained in reflected light.
The ratio (to be referred to as the “scattering characteristic” of the surface of a measurement target) of the specular reflection component and scattering component changes depending on the surface state of the measurement target.
When the surface shape of a measurement target is measured by the pattern projection method, its surface state is desirably measured together. Similarly, pattern light to irradiate a measurement target is desirably controlled in consideration of the surface state of the measurement target in order to measure the scattering characteristic indicating the surface state of the measurement target at high precision.